Precise control component for a substrate potential regulation circuit

ABSTRACT

A control circuit for substrate potential regulation for an integrated circuit device. The control circuit includes a current source configured to generate a reference current. A variable resistor is coupled to the current source. The variable resistor is configured to receive the reference current and generate a reference voltage at a node between the current source and the variable resistor. The reference voltage controls the operation of a substrate potential regulation circuit coupled to the node.

REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.10/746,539, filed on Dec. 23, 2003, which is hereby incorporated byreference in its entirety.

This application is related to U.S. patent application Ser. No.10/747,022, filed on Dec. 23, 2003, which is hereby incorporated byreference in its entirety.

This application is related to U.S. patent application Ser. No.10/747,016, filed on Dec. 23, 2003, which is hereby incorporated byreference in its entirety.

This application is related to U.S. patent application Ser. No.10/747,015, filed on Dec. 23, 2003, which is hereby incorporated byreference in its entirety.

TECHNICAL FIELD

Embodiments relate to body biasing circuits for providing operationalvoltages in integrated circuit devices.

BACKGROUND ART

As the operating voltages for CMOS transistor circuits have decreased,variations in the threshold voltages for the transistors have becomemore significant. Although low operating voltages offer the potentialfor reduced power consumption and higher operating speeds, thresholdvoltage variations due to process and environmental variables oftenprevent optimum efficiency and performance from being achieved.Body-biasing is a prior art mechanism for compensating for thresholdvoltage variations. Body-biasing introduces a reverse bias potentialbetween the bulk and the source of the transistor, allowing thethreshold voltage of the transistor to be adjusted electrically. It isimportant that the circuits that implement and regulate the substratebody biasing function effectively and precisely. Inefficient, orotherwise substandard, body bias control can cause a number of problemswith the operation of the integrated circuit, such as, for example,improper bias voltage at the junctions, excessive current flow, and thelike.

SUMMARY

Embodiments provide a control component for substrate potentialregulation for an integrated circuit device.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthis specification, illustrate embodiments and, together with thedescription, serve to explain the principles of the disclosure:

FIG. 1 shows an exemplary integrated circuit device in accordance withone embodiment.

FIG. 2 shows a diagram depicting the internal components of theregulation circuit in accordance with one embodiment.

FIG. 3 shows a diagram of a resistor chain in accordance with oneembodiment.

FIG. 4 shows a diagram of a current source in accordance with oneembodiment.

FIG. 5 shows a diagram of a stabilization component in accordance withone embodiment.

FIG. 6 shows a diagram of a positive charge pump regulation circuit inaccordance with one embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings. While the disclosure willbe described in conjunction with embodiments, it will be understood thatthey are not intended to limit the disclosure to these embodiments. Onthe contrary, the disclosure is intended to cover alternatives,modifications and equivalents, which may be included within the spiritand scope of the disclosure as defined by the appended claims.Furthermore, in the following detailed description of embodiments,numerous specific details are set forth in order to provide a thoroughunderstanding of the disclosure. However, it will be recognized by oneof ordinary skill in the art that the disclosure may be practicedwithout these specific details. In other instances, well-known methods,procedures, components, and circuits have not been described in detailas not to unnecessarily obscure aspects of the embodiments.

FIG. 1 shows an exemplary integrated circuit device 100 in accordancewith one embodiment. As depicted in FIG. 1, the integrated circuitdevice 100 shows an inverter having connections to a body-biasingsubstrate potential regulation circuit 110 (e.g., hereafter regulationcircuit 110). The regulation circuit 110 is coupled to provide body biascurrents to a PFET 102 through a direct bias contact 121, or by a buriedn-well 126 using contact 122. As shown in FIG. 1, a p-type substrate 105supports an NFET 101 and the PFET 102 resides within an n-well 115.Similarly, body-bias may be provided to the NFET 101 by a surfacecontact 121, or by a backside contact 123. An aperture 125 may beprovided in the buried n-well 126 so that the bias potential reaches theNFET 101. In general, the PFET 102 or the NFET 101 may be biased by theregulation circuit 110 through one of the alternative contacts shown.The integrated circuit device 100 employs body-biasing via theregulation circuit 110 to compensate for any threshold voltagevariations.

Additional description of the operation of a regulation circuit inaccordance with embodiments can be found in commonly assigned U.S.patent application Ser. No. 10/747,016, filed on Dec. 23, 2003, which ishereby incorporated by reference in its entirety.

FIG. 2 shows a diagram depicting the internal components of theregulation circuit 200 in accordance with one embodiment. The regulationcircuit 200 shows one exemplary component configuration suited for theimplementation of the regulation circuit 110 shown in FIG. 1 above.

In the regulation circuit 200 embodiment, a current source 201 and avariable resistor 202 are coupled to generate a reference voltage at anode 220 (e.g., hereafter reference voltage 220) as shown. The referencevoltage 220 is coupled as an input for a comparator 205. The output ofthe comparator 205 is coupled to a charge pump 210 and a stabilizationcomponent 215. The output of the regulation circuit 200 is generated atan output node 230. The output node 230 can be coupled to one or morebody bias contacts of an integrated circuit device (e.g., the contacts121-123 shown in FIG. 1).

In the regulation circuit 200 embodiment, the current source 201 and thevariable resistor 202 form a control circuit, or control component, thatdetermines the operating point of the regulation circuit 200. Thecurrent source 201 and the variable resistor 202 determine the referencevoltage 220. The comparator 205 examines the reference voltage 220 andthe ground voltage 221 and switches on if the reference voltage 220 ishigher than the ground voltage 221. The comparator output 206 turns onthe charge pump 210, which actively drives the output node 230 to alower (e.g., negative) voltage. The effect of turning on the charge pump210 is to actively drive the body bias of a coupled integrated circuitto a lower voltage. This lower voltage will eventually be seen at thereference voltage node 220 of the comparator 205. Once the referencevoltage 220 and the ground voltage 221 are equalized, the comparatorwill switch off, thereby turning off the charge pump 210. With theconstant reference current from the current source 201, the body bias ofthe integrated circuit device will thus be equal to the voltage dropacross the variable resistor 202.

Once the charge pump 210 is turned off, the body bias of the integratedcircuit device will rise over time as the numerous components of theintegrated circuit device sink current to ground. When the referencevoltage 220 rises above the ground voltage 221, the comparator 205 willswitch on the charge pump 210 to re-establish the desired body bias. Atypical value for Vdd for the integrated circuit device is 2.5 volts.

As described above, the current source 201 and the variable resistor 202determine the reference voltage 220, and thus, the operating point ofthe regulation circuit 200. The reference voltage 220 is generated by areference current flowing from the current source 201 through thevariable resistor 202. Accordingly, the reference voltage 220 isadjusted by either adjusting the reference current or adjusting theresistance value of the variable resistor 202.

In one embodiment, the reference current is designed for stability andis controlled by a band gap voltage source of the integrated circuitdevice. Thus, as the temperature of the device changes, the referencecurrent should be stable. Additionally, the reference current should bestable across normal process variation. A typical value for thereference current is 10 microamps. In such an embodiment, the referencevoltage 220 is adjusted by changing the variable resistance 202.

In the present embodiment, the stabilization component 215 functions asa stabilizing shunt that prevents over charging of the body bias. Asdescribed above, once the charge pump 210 is turned off, the body biasof the integrated circuit device will rise over time as the integratedcircuit device sinks current to ground. The stabilization component 215functions in those cases when the charge pump 210 overcharges the bodybias.

FIG. 3 shows a diagram of a resistor chain 300 in accordance with oneembodiment. The resistor chain 300 shows one configuration suited forthe implementation of the variable resistor 202 shown in FIG. 2 above.The resistor chain 300 comprises a chain of resistor elements 301-308arranged in series. In the present embodiment, a resistance value forthe resistor chain 300 is selected by tapping a selected one of theresistor elements 301-308. This is accomplished by turning on one of thecoupled transistors 311-318. For example, increasing the resistancevalue is accomplished by tapping a resister earlier in the chain (e.g.,resistor 301) 300 as opposed to later in the chain (e.g., resistor 307).The resistance value is selected by writing to a configuration register310 coupled to control the transistors 311-318.

FIG. 4 shows a diagram of a current source 400 in accordance with oneembodiment. The current source 400 shows one configuration suited forthe implementation of the current source 201 shown in FIG. 2. Thecurrent source 400 includes a band gap voltage reference 410 coupled toan amplifier 415. The amplifier 415 controls the transistor 403, whichin turn controls the current flowing through the transistor 401 and theresistor 404. This current is mirrored by the transistor 402, and is thereference current generated by the current source 400 (e.g., depicted asthe reference current 420).

In this embodiment, the use of a band gap voltage reference 410 resultsin a stable reference current 420 across different operatingtemperatures and across different process corners. The reference voltage220 is governed by the expression K*Vbg, where K is the ratio of thevariable resistor 202 and the resistance within the band gap reference410 and Vbg is the band gap voltage.

FIG. 5 shows a diagram of a stabilization component 500 in accordancewith one embodiment. The stabilization component 500 shows oneconfiguration suited for the implementation of the stabilizationcomponent 215 shown in FIG. 2. In the present embodiment, thestabilization component 500 functions as a stabilizing shunt thatprevents over charging of the body bias.

As described above, once the charge pump 210 is turned off, the bodybias of the integrated circuit device, and thus the ground voltage 221,will rise over time as the integrated circuit device sinks current toground. The stabilization component 215 functions in those cases whenthe charge pump 210 overcharges the body bias. For example, there may becircumstances where the charge pump 210 remains on for an excessiveamount of time. This can cause an excessive negative charge in the bodyof the integrated circuit device. The stabilization component 215 candetect an excessive charging action of the charge pump 210.

When excessive charging is detected (e.g., the charge pump 210 being ontoo long), the stabilization component 215 can shunt current directlybetween ground and the body bias (e.g., Vpw), thereby more rapidlyreturning the body bias voltage to its desired level. When the referencevoltage 220 rises to the ground voltage 221, the comparator 205 willswitch on the charge pump 210 to maintain the desired body bias.

In the stabilization component 500 embodiment, the output of thecomparator 205 is coupled as an input to three flip-flops 511-513. Theflip-flops 511-513 receive a common clock signal 501. The flip-flops 511and 512 are coupled in series as shown. The outputs of the flip-flops512 and 513 are inputs to the AND gate 515. The AND gate 515 controlsthe enable input of a shunt switch 520.

In normal operation, the comparator output 206 will cycle between logicone and logic zero as the comparator 205 turns off and turns off thecharge pump 210 to maintain the voltage reference 220 in equilibriumwith ground 221. Thus, the output 206 will oscillate at some meanfrequency (e.g., typically 40 MHz). The clock signal 501 is typicallychosen to match this frequency. If the comparator output 206 remainshigh for two consecutive clock cycles, the shunt switch 520 will beenabled, and current will be shunted between, in a negative charge pumpcase, between Vpw and ground, as depicted. In a positive charge pumpcase (e.g., FIG. 6) current will be shunted between Vnw and Vdd.

FIG. 6 shows a diagram of a positive charge pump regulation circuit 600in accordance with one embodiment. The regulation circuit 600 shows oneexemplary component configuration suited for the implementation of apositive charge pump (e.g., Vnw) version of the regulation circuit 110above.

The regulation circuit 600 embodiment functions in substantially thesame manner as the circuit 200 embodiment. A current source 601 and avariable resistor 602 are coupled to generate a reference voltage at anode 620 as shown. The reference voltage 620 is coupled as an input fora comparator 605. The output of the comparator 605 is controls a chargepump 610 and a stabilization component 615. The output of the regulationcircuit 600 is generated at an output node 630 and is for coupling tothe Vnw body bias contacts of an integrated circuit device.

As with the circuit 200 embodiment, the current source 601 and thevariable resistor 602 form a control circuit that determines theoperating point. The comparator 605 and the charge pump 610 activelydrive the output node 630 to force the reference voltage 620 and Vdd 621into equilibrium. With the constant reference current from the currentsource 601, the Vnw body bias of the integrated circuit device will thusbe equal to the voltage drop across the variable resistor 602.

The foregoing descriptions of specific embodiments have been presentedfor purposes of illustration and description. They are not intended tobe exhaustive or to limit the disclosure to the precise forms disclosed,and obviously many modifications and variations are possible in light ofthe above teaching. The embodiments were chosen and described in orderto best explain the principles of the disclosure and its practicalapplication, to thereby enable others skilled in the art to best utilizethe disclosure and various embodiments with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the disclosure be defined by the claims appended hereto and theirequivalents.

1. A method comprising: generating a body bias voltage; adjusting thebody bias voltage based on a voltage value representative of the bodybias voltage; and shunting the body bias voltage based on saidadjusting.
 2. The method of claim 1, wherein said generating comprises:generating a positive body bias voltage.
 3. The method of claim 1,wherein said generating comprises: generating a negative body biasvoltage.
 4. The method of claim 1, wherein said adjusting comprises:generating a reference current; and using a variable resistor, thereference current, and the body bias voltage to generate the voltagevalue.
 5. The method of claim 4, wherein said adjusting furthercomprises: comparing the voltage value with a reference voltage; andbased on said comparison, adjusting the body bias voltage.
 6. The methodof claim 1, wherein said shunting comprises: discharging an excessivenegative body bias voltage to a desired voltage level.
 7. The method ofclaim 1, wherein said shunting comprises: discharging an excessivepositive body bias voltage to a desired voltage level.
 8. A methodcomprising: comparing a voltage value representative of a body biasvoltage with a reference voltage; adjusting the body bias voltage basedon said comparing; and shunting the body bias voltage based on saidadjusting.
 9. The method of claim 8, wherein said comparing comprises:generating a reference current.
 10. The method of claim 9, wherein saidcomparing further comprises: using a variable resistor, the referencecurrent, and the body bias voltage to generate the voltage value. 11.The method of claim 8, wherein said adjusting comprises: generating apositive body bias voltage.
 12. The method of claim 8, wherein saidadjusting comprises: generating a negative body bias voltage.
 13. Themethod of claim 8, wherein said shunting comprises: discharging anexcessive negative body bias voltage to a desired voltage level.
 14. Themethod of claim 8, wherein said shunting comprises: discharging anexcessive positive body bias voltage to a desired voltage level.
 15. Amethod comprising: generating a reference current; using the referencecurrent to generate a voltage value representative of a body biasvoltage; adjusting the body bias voltage based on the voltage value; andshunting the body bias voltage based on said adjusting.
 16. The methodof claim 15, wherein said adjusting comprises: comparing the voltagevalue with a reference voltage; and based on said comparison, adjustingthe body bias voltage.
 17. The method of claim 15, wherein saidadjusting comprises: generating a positive body bias voltage.
 18. Themethod of claim 15, wherein said adjusting comprises: generating anegative body bias voltage.
 19. The method of claim 15, wherein saidshunting comprises: discharging an excessive negative body bias voltageto a desired voltage level.
 20. The method of claim 15, wherein saidshunting comprises: discharging an excessive positive body bias voltageto a desired voltage level.